The present invention generally relates to wireless communication networks, and particularly relates to generating common rate control commands at wireless base stations in such networks.
Developing standards define relatively sophisticated mechanisms for increasing the utilization efficiencies of wireless communication networks. For example, Release D of the IS-2000 standards include several Medium Access Control (MAC) layer rate control mechanisms that enable Radio Base Stations (RBS) to influence the reverse link packet data rates of mobile stations responsive to estimated reverse link loading at the RBSs. This ability allows an RBS to increase or decrease its reverse link load by driving mobile station reverse link data rates up or down as needed.
Indeed, the standards define a number of rate control mechanisms that may be used for different mobile stations, or groups of mobile stations. With such controls, the rates of some mobile stations may be driven upward, while the rates of others are driven downward. For example, Release D of the IS-2000 standards provides both Common Rate Control (CRC) and Dedicated Rate Control (DRC). DRC algorithms generate individualized rate control commands for targeted to individual mobile stations, while CRC algorithms generate group-specific rate control commands targeted to selected groups of mobile stations.
The group of mobile stations, for example, may be all mobile stations operating within a radio sector. However, CRC commands may be generated for each of potentially many different groups of mobile stations within the sector. That is, all of the mobile stations in a given group would receive the same CRC commands, but the CRC commands for each group would be generated separately. Such processing allows relatively convenient differentiation of user classes, for example.
However, even though different CRC commands can be generated for different groups of mobile stations, all CRC command generation typically is based on sector loading. As the reverse link loading increases, CRC command generation can be used to drive the reverse link data rates of one or more mobile station groups downward. Conversely, as the sector's reverse link becomes more lightly loaded, CRC command generation can be used to drive the reverse link rates of one or more mobile station groups upward.
In contrast to CRC commands, DRC commands are mobile-specific. That is, DRC commands are individually generated for specific mobile stations, thereby allowing more direct and individualized rate control for particular ones of the mobile stations operating within the radio sector. DRC commands thus might be generated for a select number of mobile stations whose Quality-of-Service (QoS) requirements might not be met using CRC, and the reverse link rate of a mobile station operating under DRC might be driven upward at the same time CRC commands are being used to drive the reverse link rates of a given mobile station group downward.
DRC command generation for a given mobile station generally relies on some form of status feedback from the mobile station. For example, Release D of the IS-2000 standard defines a reverse link rate control feedback mechanism based on a Mobile station Status Indicator Bit (MSIB). For purposes of DRC, mobile stations may return these status bits at a defined rate on the Reverse Packet Data Control Channel (R-PDCCH). Each MSIB from a given mobile station indicates whether that mobile station has enough transmit power headroom to increase its reverse link data rate, and whether it has enough pending data to go to a higher reverse link data rate—e.g., a “1” indicates that the mobile station's reverse link rate should be increased and a “0” indicates that the mobile station's reverse link rate should not be increased.